Mazda MX-5 Miata Back Up Light Bulb Size

The Mazda MX-5 Miata back up light utilizes 7440 and 921 bulb sizes for the specific lighting components. Provided information covers the span from 2006 through 2019 for the listed vehicle.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2016-2019	7440
2006-2015	921

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921

Other Locations

Additional Notes

The Mazda MX-5 Miata uses two distinct back up light bulb types across the 2006-2019 model years: the 921 (T15) and the 7440 (T20).
The 921 bulb is a T15 wedge type rated at 12V and 16W under the ANSI standard applicable to the US and Canada.
The 7440 bulb is a T20 single-filament wedge type rated at 12V and 21W, also conforming to the ANSI standard for the US and Canada.
The MX-5 Miata used the 921 bulb for the 2006-2015 model years in the back up light position.
The 7440 bulb applies to the 2016-2019 model years, representing a change in the specified bulb type relative to earlier production.
The T15 and T20 designations refer to the outer envelope width of the wedge base, with T20 being physically larger than T15. These two bulb types are not interchangeable due to differences in size and wattage.
The wattage difference between the two bulbs is notable: the 7440 draws 21W while the 921 draws 16W, meaning the newer specification calls for a higher-output bulb in the back up light circuit.
Both bulb types use a wedge base, which is a baseless design where the glass envelope itself is pinched to form the electrical contacts, eliminating the need for a separate metal base.